[Haskell-cafe] Documentation [Comments from OCaml Hacker Brian Hurt]

Andrew Coppin andrewcoppin at btinternet.com
Fri Jan 16 14:18:56 EST 2009

Anton van Straaten wrote:
> It probably makes sense to do as Jeremy Shaw suggests and explicitly 
> list the monoid laws, which would include the associative equality, 
> but there really shouldn't be any other text in the definition of 
> Monoid devoted to explaining what associativity means.  Instead, 
> linking words like "associative" to a definition in a glossary would 
> make sense.

I don't know - associativity is almost the only property a monoid has. 
(Obviously the other one is an identity element.)

Either way, wherever the description gets put, just saying 
"associativity means that (x + y) + z = x + (y + z)" is insufficient. 
Sure, that's the *definition* of what it is, but we should point out 
that "associativity means that the ordering of the operations does not 
affect the result" or something. Something that's intuitive. (The tricky 
part, of course, is explaining how associative /= commutative.)

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